1. Field of the Invention
This invention relates to casement window operators of the type in which a pivotally mounted window controlling lever is actuated by a crank or electric motor operated worm gear drive, and specifically to one having a more robust design for supporting thrust loads. More specifically, the worm gear drive operator is designed with thrust bearing components at each end of a worm gear drive to remove mechanical rotating surfaces from interaction with the housing base or cover plate, while absorbing the rotational thrust of the device. The invention further relates to a vertically adjustable actuator arm, where the adjustment may be made in-situ after installation utilizing a threaded post about which rests a bearing for the actuator arm on a hardened steel plate for thrust load support, and which is secured in place by an adjustment screw received within the threaded post.
2. Description of Related Art
A casement type window is a window that opens outward and is hinged along one side. A transparent windowpane is held in a framework, referred to as the casement window “sash,” and the sash is hinged along one edge to a fixed window frame. Because a casement window swings outward, a screen for the window must be mounted on the inside.
Mounting the screen on the inside prevents the user from directly accessing the sash to open or close the window. Thus, casement windows are commonly provided with a mechanical device, referred to as a “casement window operator.” The casement window operator is mounted at an accessible location on the inside of the window frame and functions to swing the sash open or closed without requiring the screen to be removed.
There are many different known designs for casement window operators; however, they generally all include a base mounted to the inside of the window frame, a handle mounted to the base and one or more operator arms that are driven by the handle. The driven arm or arms apply a force between the window frame and the window sash to swing the casement window sash between the open and closed positions.
Casement windows employ a sash that swings open and closed about an upright axis along one vertical edge of the sash, or sliding axis parallel to the sill and header. Operator assemblies for affecting that swinging motion have been available for many years in various forms. Generally, the casement window is opened and closed by a hand crank or electric motor. Casement window cranks usually consist of a handle, a spindle, and internal gears. Each time the handle or crank is operated via hand or electric motor, gears at the inner end of the spindle engage with larger gears that push or pull the actuator arm or crank arm that opens or closes the window.
The crank activates a worm drive that drives a worm gear which interacts with an actuator arm to push the window sash open. A worm drive is a gear arrangement in which a worm or gear in the form of a screw meshes a complementary gear structure on the actuator arm. Like other gear arrangements, a worm drive can reduce rotational speed or allow higher torque to be transmitted.
The worm gear is meshed with a gear segment which is part of the linkage assembly inclusive of an actuator arm that is connected to the sash. The worm gear and gear segment are usually accommodated within a housing or escutcheon with a shaft of the worm gear extending outward through the housing to mateably engage a handle or crank. The shaft is typically splined to achieve rotation without slipping when the handle crank is attached. When the crank is turned, the worm gear causes the gear segment and actuator arm to rotate which causes the sash to pivot on its hinges between open and closed positions.
One issue with this type of design is the limited amount of force or thrust that the operator assembly is capable of withstanding. This limited durability is especially evident under adverse environmental conditions such as high winds acting on an opened sash, which causes undue stress and strain on the operator assembly. Additionally, thrust forces associated with opening a partially blocked sash, or a sash that for other reasons remains reluctant to open, are amplified and present undue stress on the housing and worm gear drive that can cause breakage or undue degradation over a short period of time.
A second issue with this type of design is the inability to make adjustments to the operator assembly, and particularly the operator assembly actuator arm, during or after installation. A design that lends itself to adjustment during assembly would greatly benefit the manufacturer, and make for a more reliable operation since acute adjustments may be made in-situ, which may account for dimensional tolerance discrepancies upon installation.
In U.S. Pat. No. 4,860,493, issued to Lense on Aug. 29, 1989, titled “Non-Backdriving Actuator For Opening and Closing a Window Sash,” a non-back driven actuator is taught. The window shaft is automatically locked against rotation if a backdriving force is applied to the actuator from outside the premises. This prevents an open sash from being buffeted by wind and from being pulled open further by a potential intruder. The sash is supported for movement between its closed and open positions in a conventional manner. There are no additional components to compensate for the added thrust.
In U.S. Pat. No. 5,765,308 issued to Anderson, et al. on Jun. 16, 1998, titled “Window Operator,” a window operator is taught that includes a cover secured to the base with a support surface having a hole therethrough defining an internal shoulder. The second support surface mates with another support surface. A post extends from the cover and through the aperture in the base when the operator is assembled. An arm is pivotally secured to the post and attachable to the sash to control the movement of the sash between open and closed positions. A worm drive assembly driveably engages the arm and has a worm shaft and a worm shoulder disposed on the worm shaft. The worm is directly supported by the support surfaces at one end and the worm shoulder engages the internal shoulder as the worm shaft protrudes from the hole. Importantly, unlike the present invention, this design does not limit thrust force or include an adjustment screw bearing cooperating with an inner threaded post.
In U.S. Pat. No. 7,278,335, issued to Zhang on Oct. 9, 2007, titled “Adjustable Threaded Bearing and Bearing Assembly for a Window Operator and Feature,” a bearing assembly is taught for use with a window operator having a housing with an operator slot and a bore through which is threaded an adjustable bearing. The bearing contains a smooth end with two walls of differing diameter that form shoulders. The shoulders fit substantially against an inner and outer surface of the slot to rotatably position and secure an operator arm therein.
When the operator arm is inserted into the slot of the housing a gap forms between the operator arm and the upper part of the slot section. To minimize or alleviate this gap, an adjustable bearing is placed into the bore of the housing. The adjustable bearing has a generally cylindrical body with an internal end and an external threaded end. The threaded bearing is disposed through the bore and hole to mount rotatably the operator arm within housing. An external threaded end threads into an internal thread of the bore and inner end fits inside the bore extending into the top part, closed end.
The operator arm moves around the bearing, and the connector end, attached directly or indirectly to a window sash, functions for opening and closing windows. The movement of the operator arm is achieved by the close association of movement between the operator arm and the worm gear. Although there is a type of adjustment to the arm, this adjustment is not designed to be made after installation, and there is no attempt in this prior art to provide an adjustment screw with bottom bearing surface made of a hardened material to support the thrust loads on the worm gear downward.